1. Field of the Invention
The invention relates to a trigger circuit for a field-effect-controlled power semiconductor component having a conducting-state MOSFET through which a trigger signal can be delivered to the gate terminal of the power semiconductor component, in the event that the conducting-state MOSFET is conducting.
One such trigger circuit is known, for instance, from German Published, Non-Prosecuted Patent Application DE 42 05 753 A1, corresponding to U.S. Pat. No. 5,272,399. FIG. 1 thereof discloses a MOSFET 1 having a gate which is connected through a resistor 6 to a control input. A load path of a MOSFET, which is triggered as a function of the drain-to-source voltage of the power semiconductor 1, is connected between the gate and a source of the power semiconductor 1. Such a circuit configuration is used in power semiconductor components with an MOS input in order to limit the current I.sub.DS in the event of a short circuit. That kind of additional circuit in principle includes a series resistor, in the present case the resistor 6, which is needed in order to assure the current limitation.
The disadvantage of such a configuration is that the turn-on speed is limited by the serial resistor and thus becomes relatively long.
Another circuit configuration of that generic type is known from U.S. Pat. No. 5,506,539. The circuit configuration which is shown particularly in FIG. 3 thereof has a guard circuit that switches a controllable resistor to high impedance and low-impedance states. However, the circuit configuration disclosed therein is extremely expensive and complicated to manufacture.